Fiber-reinforced composites are high strength, high modulus materials which are finding wide acceptance for use as structural components in a variety of applications, such as aerospace, structural engineering, and automotive applications. In addition, these composites also have use in ballistic resistant materials, sporting goods, home appliances, pressure vessels and storage tanks, bridges, boat and scull hulls, sailboats, rowing shells, bicycle and motorcycle frames and components, swimming pools, spacecraft including satellites, concrete, heat shields, fuselages, disk brake systems, pipes and industrial materials, trains, electronic devices and equipment, musical instruments, audio components, furniture, medical equipment, windmills, civil engineering and construction related.
Typically, the composites used in structural applications comprise structural fibers in the form of continuous filaments or woven cloth embedded in a thermosetting or thermoplastic matrix. Such composites may exhibit considerable strength and stiffness, and the potential for obtaining significant weight savings makes them highly attractive for use in primary structural applications as a metal replacement. However, acceptance for many structural applications has been limited by the fact that many of the composite materials presently available are brittle. The inability of such composites to withstand impact while retaining useful tensile and compression strengths has been a serious problem for many years. Compensating for the brittleness and low impact resistance of such materials may ordinarily be accomplished by increasing the amount of material employed. This approach increases costs, reduces the weight savings that might otherwise be realized and may make them unacceptable for many uses.
The composites industry has long been involved in finding ways to overcome these deficiencies. Considerable effort has been expended over the past two decades directed toward the development of composites with improved fracture toughness. Inasmuch as most of the commonly employed matrix resins, as well as many of the reinforcing fibers, are generally brittle, much of that effort has gone into a search for component replacements having better toughness characteristics.
The round fibers used in composites fabricated today have a low surface area resulting in large voids and increased resin content when packed during manufacturing. This configuration makes the fiber-resin composite sheets less resistant to extreme bending—global and localized such as those experienced during impact events. In addition, these materials have limited tailorability.
Thus, there is a need for tough, impact resistant composite materials that offer increased property tailorability, increased damage tolerance, decreased delamination potential, decreased composite weight, and maximized mechanical interlocking.